How to search for an object within an array using MongoDB and Express.js

In my "equipos" database, the structure is as follows:

    [   
    "_id" : ObjectId("5ae4ea9f434d9b51dad68813"),
    "team_name" : "Alavés",
    "nombre_equipo_movil" : "ALA",
    "cantidad_integrantes" : 20,
    "partidos_jugados" : 29,
    "partidos_ganados" : 10,
    "partidos_empatados" : 1,
    "partidos_perdidos" : 18,
    "goles_a_favor" : 26,
    "goles_en_contra" : 45,
    "players" : [
            {
                    "dorsal" : 1,
                    "nombre_jugador" : "Fernando Pacheco",
                    "edad" : 25,
                    "nacionalidad" : "España",
                    "posicion" : "Portero",
                    "goles" : 0,
                    "asistencias" : 0,
                    "amarillas" : 4,
                    "rojas" : 1
            }
            ...
            ]
    ... 
    ]

I am trying to find out if there is a player with "dorsal" equal to 1 in the team Alavés. I have written the query as follows:

db.equipos.findOne({"team_name": "Alavés" }, {"players": {$elemMatch: {"dorsal": 1l}}})

However, the issue arises when there is no player found with dorsal 1, and the response displays the team's ID like this:

{ "_id" : ObjectId("5ae4ea9f434d9b51dad68813") }

This poses a problem for me when I try to compare the response against null using Express:

    dbo.collection("equipos").findOne(
        {"team_name": sReq.body.nombre_equipo }, {"players": {$elemMatch: {"dorsal": sReq.body.dorsal}}},
        function(err, res){

Do you have any suggestions on how I can determine if the searched player does not exist based on this type of response?

javascriptmongodbexpress

Answer №1

Experiment using .....dorsal:parseInt(sReq.body.dorsal).... – The reason being req.body.xxx is identified as a string, while dorsal is of type Number. Therefore, it is necessary to convert the string into a number using the parseInt method.

Answer №2

Instead of checking if res is equal to null, consider comparing the length of its keys by using Object.keys(res).length == 1. I'm not sure why your query is producing that particular result, but this approach might provide some clarity.

if(Object.keys(res).length == 1) {
    console.log("No player found!");
} else {
    console.log("Hey there!");
}

Answer №3

When using the Mongoose findOne method, you have the option to include a second argument specifying which fields to select.

For example, your query should look like this:

dbo.collection("equipos").findOne(
        {"team_name": sReq.body.team_name,
         "players": {$elemMatch: {"number": sReq.body.number}}
        }, function(err, res){

It's important to note that the fields you want to query should be included as the first argument, and the callback function should be passed as the second argument when not specifying the fields to select.

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